The present invention generally relates to molded plastic containers of the type commonly used for a variety of purposes including storage of both food items and non-food items, such containers preferably being adapted to receive an appropriate seal or lid. More specifically, the invention is concerned with containers of this type which, rather than being of a rigid construction as with a conventional container, are collapsible or foldable to a compact position when empty to facilitate convenient use and storage.
Such containers, in the form of tumblers, cups, bowls, and the like, are generally known in the art and take many forms. These include collapsible cups or glasses wherein the glass is formed of telescopically stacked annular wall elements which slide relative to each other between a fully extended position and a collapsed position. As the wall elements are not integrally formed and slide freely relative to each other, there is a substantial possibility of leakage, and use, other than as a temporary drinking vessel, is not practical.
One form of collapsible container is illustrated in U.S. Pat. No. 5,439,128, issued to Fishman on Aug. 8, 1995. In the Fishman container, the wall elements are integrally molded and consist of a series of vertical and angled elements alternately stacked to define the container wall. The elements, at the angular joint therebetween, are integrally joined by thin film hinges about which the wall elements fold. The actual downward folding and collapsing of the Fishman elements requires that the elements flex in order to accommodate the folding motion. This necessity for an actual flexing of the elements themselves, in addition to the folding at the film hinges, appears to be so significant as to, at least, in some instances, as illustrated in FIG. 3 of Fishman, require significant central relief grooves in each of the inclined wall elements which would appear to cause an inherent weakening of these wall elements.
Another collapsible container is illustrated in U.S. Pat. No. 7,654,402, issued to Kusuma et al. on Feb. 2, 2010. In the Kusuma container, angularly related multiple folding sections extend at an angle to the vertical, and include, within each section itself, a “flexure zone” adjacent the angular joint between adjacent sections and flexibly movable between a first open position in the expanded container and a second position folded upon itself in the collapsed container. The flexure zones resist movement of the sections in both the fully expanded container and the collapsed container, as well as any intermediate position wherein only selected flexure zones are in an open position. One disadvantage of this arrangement, however, is that, as the diameter of the opening in the container decreases, the amount of force required to collapse or expand the container increases to the point of being less practical to use. The Kusuma container is therefore best suited for containers having a relatively large diameter.
Another form of collapsible cup more pertinent to the present invention is illustrated in U.S. Pat. No. 2,880,902, issued to Owsen on Apr. 7, 1959. In the Owsen cup, the wall elements are integrally molded in a single molding step, and comprise a plurality of annular and relatively thick wall sections alternating with annular thin wall sections, all of which are of successively decreasing diameter from the top to the bottom of the cup. Due to the fact that the body is made of a flexible plastic material, the thin wall sections are relatively more flexible than the thick wall sections, and each thin wall section will consequently reversely move over itself into an inside out or inverted position, when the thick wall sections of different diameters are moved into telescopic relation. With the single molding step described by Owsen, however, there is no possibility to obtain an optimal hardness to softness ratio for the annular sections of a collapsible cup, which can be achieved through the use of two different materials in a multiple injection molding process.
A collapsible container is also shown in U.S. Pat. No. 5,575,398, issued to Robbins, III on Nov. 19, 1996. The Robbins, III container is also extrusion or blow molded in a single molding step, and comprises a bottom wall and relatively flexible peripheral side walls extending upwardly from the bottom wall, the side walls being connected by areas of reduced side wall thickness, to facilitate the collapsing of the container.
A collapsible container has not heretofore particularly lent itself to formation from two materials of differing hardness, flexibility, or rigidity, in the collapsible section of the container. This allows the container to be collapsed with less force than is required for existing containers having a collapsible section comprised of only one type of material, and is particularly desirable where the container is to be used by children or elderly persons having limited mobility or dexterity in their hands and/or fingers.